Field of the Invention
The present invention relates to a device for sterilizing microorganisims. In particular, it relates to a device for treatment of a patient for the purpose of killing microorganisms.
Description of Related Art
Microbiological sterilization has been pivotal in the production of biological products with extended storage times. Various technologies have been developed to achieve this sterilization, including UV-irradiation, gamma-ray irradiation (or gamma irradiation), chemical sterilization, heat sterilization, autoclaving, and ultrafiltration. Because these technologies destroy microorganisms, they are inherently damaging to other biological components that may be in the product to be sterilized. In light of this fact, a particular technology may not always be acceptable for sterilizing a given biological product. Recently, an increase in the number and variety of biotechnology products has created a need for adequate sterilization without the damaging side-effects to the desirable components of the product. These biotechnology products are often extremely labile, requiring special handling and storage conditions to retain their activity. Of the sterilizing technologies previously cited, several are not acceptable for these biotechnology applications. Chemical sterilization, heat sterilization, and autoclaving all damage or alter biological molecules, rendering them inactive. The inactivation of biological molecules effectively kills the microbe that utilized these molecules for life processes. However, this inactivation of biological molecules that occurs with prior art technologies is inherently problematic in that it may also inactivate the desired molecule or molecules contained in the biotechnology product, thus defeating the purpose of the sterilization.
Ultrafiltration, a recent technology relative to the others mentioned here, requires the use of filters with a very minute pore-size (at least <0.45 microns). These filters are an inherently slow means of sterilization, and may not be suitable for solutions of high viscosity or solutions that contain desirable particles, such as cells, that are larger than the pore diameter and, consequently, too large to pass through the filter. Gamma-irradiation is a technology not commonly used for microbial sterilization, although it can be used to ensure the sterility of the majority of, if not all, biotechnology products. One major reason for its lack of widespread use for microbial sterilization is that it utilizes a radiation source, such as radioactive cobalt, that is very radioactive, and thus, very dangerous. This technology requires extensive shielding and control systems to prevent accidental exposure to operators and others. These protective requirements are economically expensive, often prohibitively so. Therefore, gamma-irradiation is often not an economically acceptable technology or a safe technology for sterilization of biotechnology products. Additionally, gamma-irradiation sterilizes products by lysising the biological molecules contained in microorganisms. This photochemical mechanism of sterilization may also degrade the desired product, rendering it inactive, and thus defeating the purpose of the sterilization.
UV-irradiation has been used extensively for microbial sterilization. UV light breaks the hydrogen bonds between adenine-thymine moieties in the DNA polymer that comprises the genome of the cell or virus, and catalyzes the formation of a cyclobutane dimer between adjacent thymine moieties. This disruption of the genome blocks the replication cycle of the cell or virus, effectively inhibiting growth of the organism.
Generally, devices that use UV light to sterilize products are composed of a power supply (ballast), a UV light source, a light-focusing and/or light-conducting device, a light filter, and a control system to assure proper operation. The ballast is designed to supply power to the lamp in a reliable fashion in order to ensure continuous optimal function of the lamp. A variety of UV light sources exist and are known in the prior art, including pulsed, gas-filled flash lamps, spark-gap discharged apparatus, or low-pressure mercury vapor lamps. Traditionally, low-pressure mercury vapor lamps have been used for microbial sterilization devices because these lamps are relatively inexpensive to operate and emit relatively higher amounts of UV irradiation than other sources. Other types of vapor lamps are also used, including mercury-xenon (HgXe) lamps. In particular, a preferred embodiment, according to the present invention, employs a pencil type Hg(Ar) spectral calibration lamp. These lamps are compact and offer narrow, intense emissions. Their average intensity is constant and reproducible. They have a longer life relative to other high wattage lamps. Hg(Ar) lamps of this type are generally insensitive to temperature and require only a two-minute warm-up for the mercury vapor to dominate the discharge, then 30 minutes for complete stabilization.
By way of background, light is conventionally divided into infrared light (780 nm to 2600 nm), visible light (380 nm to 780 nm), near UV light (300 nm to 380 nm), and far UV light (170 nm to 300 nm). Most UV lamp sources emit light at discrete wavelengths and include filters to filter out or block wavelengths other than the specific UV wavelength, especially 254 nm. In the UV region, the most notable UV emission occurs at 254 nm. It is known that mercury vapor lamps emit radiation at 254 nm. This wavelength can damage the genome of cells and viruses, thus inhibiting their replication, thereby sterilizing the cells and viruses. Therefore, generally in the prior art, a single wavelength detector, tuned to 254 nm, has been used to determine the amount of UV radiation reaching the target. In order to optimize the UV light output efficiency of the lamp source, at least one filter was interposed in the light path in order to block non-UV light from reaching the target, allowing only UV and proximate-UV light to reach to target. Therefore, the industry has evolved over time with the solidly established paradigm that 254 nm is the sole and exclusive wavelength of importance for UV sterilization. As such, the prior art teaches away from the inclusion of non-UV wavelength light for microbial sterilization apparatus. Furthermore, this paradigm not only teaches that polychromatic or broad spectrum light as irrelevant or unimportant, but disadvantageous.
In sharp contrast to UV irradiation, which utilizes a photo thermal and/or photochemical mechanism, Dunn (U.S. Pat. No. 4,871,559, issued Oct. 3, 1989 to Dunn et al., titled METHODS FOR PRESERVATION OF FOODSTUFFS) teaches that the inactivation of enzymes by visible and infrared radiation utilizes a photo thermal mechanism. When applied at high-intensity and in combination, UV, IR, and visible light, which are components included in a complete spectrum, result in significant shelf life and stability enhancements of food products by the killing of microbes and by the inactivation of degradatory enzymes. Notably, the prior art for UV sterilization in biotechnology applications teaches away from Dunn's approach to multiple component light application; since the prior art teaches that filtered UV light is desirable while nonfiltered UV light is undesirable for sterilization of microorganisms, prior art teaches away from the use of non-filtered UV light for the sterilization of microorganisms. Disadvantageously, the activities of biotechnology products are frequently based on enzymatic activity or require the tertiary or quaternary structure of proteins for activity. Therefore, sterilization techniques like Dunn, that indiscriminately degrade proteins and enzymes in the process of sterilization, are not acceptable for use with biotechnology products. Thus, there remains a need for a sterilization technique that can effectively sterilize a biological product without denaturing the active biological products.
Therefore, there remains a need not solved by the prior art to more effectively sterilize a biological product of microorganisms without excessive denaturing of the active biological molecules.